Polyphenyl thioethers



United States Patent ()1 3,311,665 POLYPEENYL TI HOETHERS John Robert Campbell, Tarkio, and Roger E. Hatton, Kirlrwoorl, Mo., assignors to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Original application Feb. 26, 1963, Ser. No. 261,470. Divided and this application Oct. 8, 1965, Ser. No. 494,271

3 Claims. (Cl. 260-609) This application is a division of application Ser. No. 261,470, filed Feb. 26, 1963 which in turn is a continuation-in-part of application Ser. No. 253,253, filed Jan. 23, 1963, and now abandoned; and a continuationin-part of application Ser. No. 225,869, file-d Sept. 24,

1962, which issued as US. Patent No. 3,119,877; which in turn is a continuation-in-part of application Ser. No. 202,956, filed June 18, 1962; which in turn is a continuation-in-part of application Ser. No. 161,422, filed Dec. 22, 1961; application Ser. No. 69,559, filed Nov. 16, 1960; application Ser. No. 69,574, filed Nov. 16, 1960; and application Ser. No. 69,575, filed Nov. 16, 1960, all of which are now abandoned.

Although functional fluids have long been known and widely used, the functional fluids of today are used under a wide variety of conditions which impose a severe restriction upon their physical and chemical properties. Thus, today, functional fluids are used as synthetic lubricants for gas-turbine engines, as hydraulic fluids for supersonic aircraft and missiles, as coolants for electronic equipment, etc., and in such uses are required to function at temperatures from below F. up to temperatures of 500 F. or higher. The requirement of such a wide liquid range poses the very difficult problem of finding materials which are thermally stable at very high temperatures, but are still fluid at low temperatures. In addition, such materials, or fluids, must also possess at least adequate tem perature-viscosity properties and suitable lubricity; i.e., the fluids must not get too thin at the very high temperatures nor too thick at the low temperatures, and must be able to provide minimal lubrication over the range of temperatures at which they are used.

Many materials have been proposed for use as lubricants but for most part each of them inherently possesses one or more shortcomings making their use undesirable in that respect. For example, the siliconefluids are extremely stable at high temperature but are nortorious for their poor lubricating properties. Ester lubricants on the other hand are excellent where low operating temperatures are concerned due to their low pour points and high viscosity indices, but they do not have satisfactory thermal or oxidative stability at temperatures of the order of' 400 F. and above. Mineral lubricating oils which exhibit satisfactory low-temperature viscosities have generally been found to have flash points that are dangerously low and high-temperature viscosities that are below those required. It has also been found that in general, additives do not enhance these essential properties to a satisfactory extent.

One of the most important properties that any lubricant must possess in addition to those normally associated with lubrication, such as a suitable viscosity and sufficient lubricity, is a combination of high temperature stability and oxidation stability. The latter property constitutes a basic and essential attribute which can be satisfied in one of two ways and preferably a combination of both, which are an inherent stability against degradation due to oxidation and the ability of the lubricant to respond to stabilization against oxidation in the presence of additive materials. Attemperatures up to about 400 F.,

the stabilization of organic materials is not regarded as being especially difiicult since many compounds are 3,311,665 Patented Mar. 28, 1967 known and available which will provide the needed stability. However, as temperatures are raised, such as in the operation of gas-turbine engines, there is a drastic change in the course of oxidation and the ability of known compounds to prevent oxidation of organic materials rapidly decreases. In fact, the rate of oxidation accelerates rapidly as temperatures are raised and many compounds which normally provide oxidation stabilization at lower temperatures reverse their roles at elevated temperatures and become pro-oxidants.

Recent studies in the synthetic lubricant field have indicated that polyphenyl ethers have excellent thermal stability and possess sufiicient oxidation resistance as an inherent characteristic to allow their use at extremely high operating temperatures. Unfortunately, however, even these stable materials are of limited utility when the temperatures exceed about 550 F. for long periods of time. Another disadvantage of the polyphenyl ethers is that their melting points are high so that the liquid range or range of useful operation is hampered. Another class of compounds, the poly(phenoxy)biphenyls, possess lower melting points than the polyphenyl ethers, and are, therefore, useful for lower temperature applications.

It has now been found that (1) certain all meta-linked polyphenyl thioethers inherently possess the requirements mentioned above making them outstanding materials for use as high-temperature hydraulic fluids, lubricants, heattransfer fluids, and the like, having a wide liquid range and that (2) polyphenyl thioethers and phenylmercaptobiphenyls can be used as additives for the polyphenyl ethers and phenoxybiphenyls to improve the oxidation stability thereof. Among the all meta-linked polyphenyl thioethers of this invention, m-bis (phenylmercapto)benzene is outstanding, as will be hereinafter evident.

The all meta-linked polyphenyl thioethers of this invention can be represented by the structure where n is a whole number from 1 to 3. Thus, the all meta-linked polyphenyl thioethers are:

m-Bis (phenylmercapto benzene Bis (m-phenylmercaptophenyl) sulfide m-Bis (m-phenylmercap-tophenylmercapto) benzene The term polyphenyl thioether means a compound or physical or isomeric mixtureof compounds represented by the structure ime Example 1 Into a suitable reaction vessel fitted with conventional accessories, there were charged 19.6 parts of 86% potassium hydroxide, 33 parts of thiophenol, and 120 ml. of dimethylacetamide. The resulting mixture was heated, with agitation, to remove all the water present, leaving a solution of potassium thiophenolate in dimethylacetamide. To this mixture there were then charged 26.3 parts of m-dibromo benzene, and the resulting mixture was heated to and maintained at reflux, with agitation, for about 6 hours. Thereafter water was added, resulting in the formation of an aqueous and an organic layer. The organic layer was separated, washed with water, and dried under vacuum to leave a residue which, upon fractionation, gave 32.5 parts of a light yellow oil, m-bis(phenyl mercapto)benzene, which had a boiling point of 174- 181 C. at 0.3 mm. and an index of refraction, n of 1.6742.

FOUR AROMATIC RINGS The four ring polyphenyl thioethers can be prepared by reacting an alkali metal salt of a phenylmercaptobenzenethiol with a halophenyl phenyl sulfide in dimethylacetamide or other suitable solvent, as illustrated below.

Example 2 Into a suitable reaction vessel containing a Grignard reagent of 63.4 parts of m chlorophenyl phenyl sulfide in tetrahydrofuran, there were charged 9.2 parts of sulfur. The resulting mixture was kept below 35 C. with an ice bath while stirring for about 5 minutes. Thereafter the reaction mixture was treated with dilute acid and Was Example 3 Into a suitable reaction vessel there were charged 72.5 parts of 85% potassium hydroxide, 121 parts of thiophenol and 500 ml. of dimethylacetamide. The resulting mixture was heated, with agitation, to remove the water Water was then added, resulting in the formation of an aqueous layer and an organic layer. The organic layer was separated, washed with water and dried under vacuum to leave a residue which upon fractionation gave 113.3 parts of a light yellow oil, 1,2,4-tris(phenylmercapto) benzene, boiling point 243-248 C. at 0.2 mm.

Example 4 In the manner of Example 3 potassium thiophenolate in dimethylacetarnide was prepared from 32.6 parts of potassium hydroxide, 55 parts of thiophenol and 200 ml. of dimethylacetamide. At a pot temperature of about C., 57.6 parts of ar-chloro-ar-chlorobipl1enyl were charged and the reaction mixture was then heated to and maintained at reflux, with agitation, for about twenty-four hours. The solvent was then distilled and water and ether were added to the residue. The resulting organic phase was separated, washed with water and dried to leave a residue, which upon distillation gave 46.3 parts of a light yellow viscous oil, bis (phenylmercap-to)biphenyl, boiling point 205-250 C. at 0.25 mm.

The other phenylmercaptobiphenyls of this invention are prepared in the same manner, that is, by reacting a halogenated biphenyl, preferably a chlorinated biphenyl, with an amount of a salt of a thiophenol necessary for reaction with the number of halogen atoms present.

FIVE AROMATIC RINGS T he five ring polyphenyl thioethers can be prepared by reacting an alkali metal salt of a phenylmercaptobenzenethiol with a dihalobenzene in dimethylacetatrnide or other suitable solvent, as illustrated below.

Example 5 In the manner of Example 4, 59 parts of the potassium salt of m-mercaptophenyl phenyl sulfide were reacted, in dimethylacetamide, with 15.3 parts of m-dichlorobenzene to provide m-bis(maphenylmercaptophenylmercapto)benzene, an orange liquid, B.P. 300308 C./0.18 mm.

The unique properties of the all meta-linked polyphenyl thioethers of this invention which make them outstanding materials for use as synthetic lubricants and the like are their wide liquid range, good thermal and oxidation stability, adequate lubricity, good viscosity characeteristics, etc., which can best be realized by comparison to other materials which have been suggested for such purposes. Accordingly, the melting point, boiling point and viscosity of the all meta-linked polyphenyl thioethers, other polyphenyl thioethers and phenylmercaptobiphenyls and other materials are given in the tables below.

TABLE I.-]? ROPE RTIE S Melting Boiling Viscosit cs. Lubricant Point, Point, F./

F. mm. Hg.

40 F 20 F. 100 F. 210 F m-B is(phenylmercapto)benzene -40 428/0. 3 35, 000 8, 647 12. 4 3. 05 m-Bis(phenylmercaptophenyl)sulfide 500/0. 5 11, 307 50. 8 5. 92 m-Bis(m-phenylmercaptopheuylmercapto)beu- 147 580/0. 18 270 12. 5

I zene.

13-13 is (phenylmercapto) benzene 82 o-Bis(phenylmercapto)benzene 185/0. 25 28. 25 4. 03 o-Bis(phenoxy)benzene 203 2. 98 m-Bis(phenoxy) benzene 141 2. 62 p-Bis(phenoxy)benzene 171 2. 76 m-B is(phenoxy'phenyl) ethel: 106 467/2. 6 62. 0 6. 00 pB1s(phenoxyjpl1enyl)etl1er 229 419/0. 5 Solid m-B 1s(m-phenoxyphenoxy)benzen 109 560/25 337 12. 7 p-Bis(p-phenoxyphenoxy)benzene, 301 609/10 Solid 1,2,4-tn's(phenylrnereapto)benzene- .r 475/ 0. 2 217 9. 40 Bis(phenyhnercapto)biphenyl 401-482/0. 25 19. 03

l Liquid 0 F.

present, leaving a solution of potassium thiophenolate in dimethylacetamide. At a pot temperature of about C., 54.5 parts of 1,2,4-trichlorobenzene were added. Thereafter the reaction mixture was heated to and maintained at reflux, with agitation, for about eight hours.

The oxidation stability of the all meta-linked polyphenyl thioethers can be realized by reference to the table below showing the results obtained by testing various compositions for oxidation stability using a modification of Method 5308.4, Corrosiveness and Oxidation Stability of Light Oils, contained in Federal Test Method Standard 791, Lubricants, Liquid Fuels and Related Products. The modification referred to involved increasing the temperature at Which the test is run from 347 F. (as specified in said method) to 500 F. Data from the above-mentioned test is reported in terms of percent viscosity increase for oxidation stability, that is, the percent change in viscosity of a test composition relative to the original viscosity.

phenoxybiphenyl compositions of this invention can be obtained by the addition to the polyphenyl ethers of from about 0.01% by weight to about 10% by weight of polyphenyl thiocther, as described above. As evidence of such improvement in oxidative stability, there is presented in the table below data obtained from testing various polyphenyl ether and phenoxybiphenyl compositions for oxidation stability using the modification of Method 5308.4 described above.

TABLE IV.OX1DATION STABILITY [600 F., 48 hours] Percent Additive Viscosity increase Base Composition Concen- Narne tratiton, 100 F. 210 F.

percent Mixture of five-ring polyphenyl ethers, comprising by None Control 83 32 weight about 65% m-bis (m-phcnoxyphenoxy)bcnm-Bis(phenylmercapto)benzene 0.5 54 21 zcne; 30% m-[(ni-phe11oxyphe11oxy) (pphcnoxyphenm-Bis(phenyl1nercnpto)benzene. 1.0 45 17 oxy)]benzene; 5% m-bis(p-phenoxyphenoxy)benzene. rn-Bis(phenylmercapto)benzene 2.0 48 19 m Bis(phenylmercapto)benzene 3. 0 53 20 p-Bis(phenylmercapto) benzene 2. 0 42 16 p-Bis(phenylmereaptophenyl)sulfide. 1. 5 71 m-Bis(phe11ylmereaptophenyl)sulfide 1. 0 25 9 m-B is (m-phenylmercap tophenylmercapto)benzene 1. 0 46 16 1, 2, 4-tris(phenylmercapto)benzene 1.0 34. 2 11. 5 o-Bis(phenyln1ercapto)benzene 1.0 33. 5 10. 2 Bis(phenylmercapto)biphenyl 1. 0 50. 5 17. 0 Mixture of four-ring polyphenyl ethers None Control 959 196 m-Bis(phenylmercapto)benzene 1. 5 13 m-Bis(m-phenoxyphenoxy)phenyl ether None Control 110 m-Bis(phenylmercapto)benzene 1. 5 90 31 TABLE II.OXIDATION STABILITY [500 F., 48 hours] Percent change in Viscosity Lubricant m-Bis(phenylmercapto)benzene 83 25 Silicone oil 93 63 Sil'me 1, 060 470 Sebaeate ester Infinite Infinite Highly refined mineral oil Infinite Infimte Scar Diameter, mm. Lubricant m-Bis(phenylmercapto)benzene 0. 46 1. 95 Silicone Oil 3.15 4. 05 Silane 3. 45 Seized Sebacate ester 0.7 Highly refined mineral oil 0.51

From the above data it is evident that the all metalinked polyphenyl thioethers are unique compounds which in addition to possessing a wide liquid range Without suffering from the poor viscosity characteristic of the polyphenyl ethers, are oxidatively stable and have good lubricating properties.

As mentioned above the polyphenyl thioethers and poly(phenylmercapto)biphenyls are, in addition to their usefulness as functional fluids, also useful as antioxidants in the polyphenyl ethers and phenoxybiphenyls. Thus, by the incorporation of the polyphenyl thioethers, the useful life of such materials at a selected temperature is greatly extended. The improved polyphenyl ether and It has also been found that m-bis (phenylmercapto)benzene, in addition to being useful as a functional fluid is also useful as a pre-emergent herbicide for various grasses, including rye grass and brome grass, a property not possessed, for example, by either por o-bis(phenylmercapto)benzene or m-bis(phenoxy)benzene. Additionally, m-bis(phenylmercapto)benzene is useful as an insecticide giving one hundred percent kill of mites by contact application in their mobile, resting and ova stages at a concentration of 0.1%.

It is also contemplated that other additives can be added to the compositions of this invention; such as pour point depressants, crystallization inhibitors or suppressants, viscosity index improvers, dyes, rust inhibitors, other oxidation inhibitors and materials to improve the lubrcation properties, especially the extreme pressure properties.

Other modes of applying the principles of this invention will be apparent to those skilled in the art. Accordingly, while this invention has been described by reference to various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A phenylmercaptobiphenyl represented by the strucwhere x and y are Whole numbers from 0 to 3 and the sum of x+y is from 1 to 6.

2. Bis (phenylmercapto biphenyl.

3. 2,2,4,4'-tetra(phenylmercapto)biphenyl.

No references cited.

CHARLES B. PARKER, Primary Examiner.

DELBERT R. PHILLIPS, Assistant Examiner. 

1. A PEHNYLMERCAPTOBIPHENYL REPRESENTED BY THE STRUCTURE 